Image forming apparatus, determination apparatus, and control method

Abstract

An image forming apparatus includes a fixing device, an image reading unit, and a control unit. The fixing device includes a heating elements arranged in a main scanning direction, a band-shaped thin film which slides on the surface of the heating element while in contact with the heating element, and a rotatable body configured to press against a surface of the thin film to cause the thin film to rotate. The fixing device heats the heating elements when an inspection sheet is passed through the fixing device, the inspection sheet having plural images formed by using a decolorable developer, each of the images having an image density that differs in a sub-scanning direction of the image forming apparatus. The image reading unit reads an image of the heated inspection sheet and the control unit determines an operative state of each heating element based on the read image.

What is claimed is: 
     
       1. An image forming apparatus, comprising:
 a heater arranged in a main scanning direction of the image forming apparatus; 
 a film configured to slide on an outer surface of the heater; 
 a rotatable member configured to press against a surface of the film; 
 an image reading unit; and 
 a control unit configured to:
 control the heater to heat an inspection sheet passing through a nip between the film and the rotatable member, the inspection sheet having an image formed thereon using a developer that becomes decolored by heating, the image having image density differences in a sub-scanning direction, 
 control the image reading unit to read the image on the heated inspection sheet, and 
 determine an operative state of the heater based on the image read by the image reading unit. 
 
 
     
     
       2. The image forming apparatus according to  claim 1 , wherein the image extends in the sub-scanning direction. 
     
     
       3. The image forming apparatus according to  claim 2 , wherein the image is formed at a first position with a first image density, a second position with a second image density less than the first image density, and a third position with a third image density less than the second image density. 
     
     
       4. The image forming apparatus according to  claim 3 , wherein the first position, the second position and the third position are aligned with respect to the main scanning direction. 
     
     
       5. The image forming apparatus according to  claim 4 , wherein the first position is adjacent to the second position in the sub-scanning direction, and the second position is adjacent to the third position in the sub-scanning direction. 
     
     
       6. The image forming apparatus according to  claim 3 , wherein a color of the image at the first position is black, and colors of the image at the second and third positions are not black. 
     
     
       7. The image forming apparatus according to  claim 1 , wherein the heater comprises a plurality of heating elements arranged in the main scanning direction. 
     
     
       8. The image forming apparatus according to  claim 7 , wherein the control unit determines an operative state of a heating element to be in a failed state if the read image at a position corresponding to the heating element contains an image density that is greater than or less than a reference image density by greater than or equal to a threshold amount. 
     
     
       9. The image forming apparatus according to  claim 8 , wherein the control unit determines an operative state of each of the heating elements based on a plurality of images read by the image reading unit. 
     
     
       10. The image forming apparatus according to  claim 1 , further comprising:
 an image forming unit configured to form the image, wherein the image formed by the image forming unit is fixed on the sheet by the nip between the film and the rotatable member. 
 
     
     
       11. A method for determining an operative state of a heater of an image forming apparatus, the heater being arranged in a main scanning direction of the image forming apparatus, and the image forming apparatus comprising a film configured to slide on an outer surface of the heater and a rotatable member configured to press against a surface of the film, the method comprising:
 heating an inspection sheet passing through a nip between the film and the rotatable member; 
 forming an image on the inspection sheet using a developer that becomes decolored by heating, the image having image density differences in a sub-scanning direction; 
 reading the image on the heated inspection sheet; and 
 determining the operative state of the heater based on the image read from the heated inspection sheet. 
 
     
     
       12. The method according to  claim 11 , wherein the image extends in the sub-scanning direction. 
     
     
       13. The method according to  claim 12 , wherein the image is formed at a first position with a first image density, a second position with a second image density less than the first image density, and a third position with a third image density less than the second image density. 
     
     
       14. The method according to  claim 13 , wherein the first position, the second position and the third position are aligned with respect to the main scanning direction. 
     
     
       15. The method according to  claim 14 , wherein the first position is adjacent to the second position in the sub-scanning direction, and the second position is adjacent to the third position in the sub-scanning direction. 
     
     
       16. The method according to  claim 13 , wherein a color of the image at the first position is black, and colors of the image at the second and third positions are not black. 
     
     
       17. The method according to  claim 11 , wherein the heater comprises a plurality of heating elements arranged in the main scanning direction. 
     
     
       18. The method according to  claim 17 , further comprising:
 determining an operative state of a heating element to be in a failed state if the read image at a position corresponding to the heating element contains an image density that is greater than or less than a reference image density by greater than or equal to a threshold amount. 
 
     
     
       19. The method according to  claim 18 , further comprising:
 determining an operative state of each of the heating elements based on a plurality of images read from the heated inspection sheet. 
 
     
     
       20. The method according to  claim 11 , wherein the image formed on the inspection sheet is fixed on the sheet by the nip between the film and the rotatable member.